5 replies to this topic

[Mike_VanOsten]

Hey guys, I recently purchased a ESR ballast system and I'm having trouble figuring out the thread pitch of the mount holes in the chassis. I've tried m12x 1.75/1.5/1.25 but none work. I'm assuming that I need to chase the threads but I'm not sure the thread pitch. Does anyone know the thread pitch for the passenger sear mount holes on a 1997?

[Alberto]

I ran into that problem once...  I don't recall the thread pitch for the seats but the seat belt sizes are an industry standard 7/16-20. Do the bolts for the seat belt fit the seat mount?  

[Mike_VanOsten]

I'm not sure as I've purchased the car as a race car, so no seat belts. Thanks for the tip on 7/16-20, I may try that lol. A friend suggested a thread restorer kit so I may bark up that tree. Thanks for the reply.

[Ron Alan]

They are 12x1.75(I believe). Same as your brake bracket bolts...very common bolt on car. Sometimes making your own tap is all you need. Put a bolt in a vise  and cut 3 or 4 slots perpendicular to the threads...parallel with bolt.  Lay a hacksaw at 30 degrees until you cut 4-6 threads up bolt. 

 

Not sure if there are any stock SAE threads on a miata as Alberto mentioned?

[Alberto]

I'm not sure as I've purchased the car as a race car, so no seat belts. Thanks for the tip on 7/16-20, I may try that lol. A friend suggested a thread restorer kit so I may bark up that tree. Thanks for the reply.

 

Careful with the tap.  You don't want to open up the threads.  There is something funky about the the thread pitch on the seats but I can't remember exactly what it is.  Don't try to force a bolt in there.  Would be difficult to repair those threads...

 

You can get OE bolts pretty cheap if you can't find the proper bolts.  I've bought PPF bolts from Blake at http://isellmiataparts.com/ very inexpensively.  I'd offer to ship you some but I don't have any extra.  You can probably also find someone on craigslist stripping a car locally.

[Mike_VanOsten]

Looks like 7/16-20 worked, thanks for the help guys.